It is well established that a key economic factor involved in the shipping of containers is the speed by which containers are loaded, unloaded and moved around a container yard. Recently inventions relating to the engagement and movement of more than one container have been suggested.
A characteristic of these multi-container devices is the problem of maintenance and the length of “downtime” of this capital intensive equipment. An example is described in WO03/104132, the contents of which are incorporated herein. If a problem arises with one of the head blocks, it is necessary to remove the entire device from the crane including disengaging the cables from the sheaves. As the separation mechanism between the head blocks uses a considerable number of actuators, this may be a significant cause of maintenance problems. If the repair or maintenance requires a workshop, the entire device must be removed from the crane by unthreading the cables. The time taken to remove and then replace the device on the crane, so as to make the crane functional, is considerable leading to significant loss of lifting capacity.
Another drawback of these types of devices is the complexity that goes into their manufacture. Typically they are large complicated devices requiring significant engineering and control over the large number of actuators involved with their operation. For instance, there are seven or more actuators required to operate the device shown in WO03/104132 (see FIG. 2). The control system or operator control needs to be complex in order to operate the device, not only for separation of the containers attached to the head blocks, but also to change their relative position, such as by “skewing” the containers, which requires operation of one set of actuators only.
It would, therefore, be advantageous to have a device which may improve the maintenance issues of said devices.